The present invention relates to a non-tracking audio and video data recording and reproducing technique and, more particularly, to such technique in which audio and video data are recorded over one or more tracks of existing data on a video tape or the like and reproduced therefrom without tracing existing tracks.
Audio and/or video data may be recorded in helical tracks of a video or VTR (video tape recorder) tape by recording heads having respective azimuth angles. Such arrangement enables the azimuth angles associated with the helical tracks to be alternated such that adjoining helical tracks do not have the same azimuth angle. During a reproduction operation, if a helical track having a first azimuth angle is scanned (traced) by a playback head having a second azimuth angle which is different from the first azimuth angle, audio and video data may not be properly reproduced from such helical track. Further, during such reproduction operation, even if a helical track is traced by a playback head having the same azimuth angle as that of the helical track, the reproduced audio and video data may have a relatively large error when the playback head and the helical track deviate from each other.
The above-described principals of azimuth recording and reproducing may apply to a so-called non-tracking type of video or VTR apparatus. Such apparatus may include two playback heads having a positive azimuth angle (positive azimuth heads) and arranged so as to have an interval substantially equivalent to the width of one helical track at the tape travelling surface of a drum, and two playback heads having a negative azimuth angle (negative azimuth heads) and arranged so as to have an interval substantially equivalent to the width of one helical track at, for example, symmetrical positions about the center of rotation of the positive azimuth heads and the drum. In such non-tracking VTR apparatus, the helical tracks may be scanned by the four playback heads so as to read the audio and video data. Such apparatus may further process the read audio and video data to detect errors and correct them using an inner code, assign a high priority to the audio and video data wherein no error was detected and corrected by use of the inner code and assign a lower priority to the audio and video data in which an error occurred and store them in a memory, correct an error or errors in the audio and video data by using an outer code, and output the audio and video data having the least error.
Since, in the above-described non-tracking VTR apparatus, audio and video data obtained by either of the two positive or two negative azimuth heads which are offset from each other by an amount of one track may be output, tracking control of a helical track by the playback heads may be greatly eased such that audio and video data may be recorded without scanning an already existing helical track (underlying track) of the VTR tape.
However, when performing an editing operation by using the above-described non-tracking VTR apparatus which records audio and video data without tracing underlying tracks, there is a possibility that the underlying tracks which are to be overwritten by the first and last tracks of the overlying tracks may remain. Upon such occurrence, if the azimuth angles of the first and last overlying tracks coincide with the azimuth angles of the underlying tracks on which such overlying tracks are to be over-written, both the audio and video data of the overlying tracks and the audio and video data of the underlying tracks may be reproduced during a reproduction operation, thereby resulting in significant error in the reproduced audio and video data.